The California Public Utilities Commission has begun a process that will allow it to add a new area code in the current 415 area code zone.

The CPUC was considering adding a 628 area code because all of the available three-digit prefixes in the 415 area code will be used up by October 2015.

When there are no more prefixes available for assignment, more numbers must be made available, and this means the addition of another area code, the CPUC said in a fact sheet on its website.

The 415 area code is currently used in San Francisco, most of Marin County and parts of San Mateo County.

The Federal Communications Commission's North American Numbering Plan Administration and the CPUC determine the best way to introduce the new area code through a lengthy planning process.

The CPUC can either divide the 415 area into two parts, forcing some residents to switch area codes, or assign the new 628 area code to new numbers, CPUC spokesman Christopher Chow said. The decision will be made after public hearings and reviews of written comments.

Chow said the process will probably take a year to complete.

The new code must be introduced at least six months before the existing code uses up all its prefixes, according to the CPUC.

The CPUC has scheduled public hearings on the matter for Jan. 16 at its auditorium in San Francisco and on Jan. 17 at the San Rafael City Council chambers.